1. Field of the Invention
The present invention relates to an image forming apparatus, which is typified by a copying machine and a laser beam printer, provided with a document reading apparatus, which is typified by an automatic document feeder (ADF) unit.
2. Description of the Related Art
With a conventional image forming apparatus of this type, a document conveyance path for conveying a document to a document reading unit, and a recording material conveyance path for conveying a recording material to an image forming unit are configured independently of each other. Specifically, a sheet feed unit, guide members, which form a predetermined conveyance path, a plurality of conveyance rollers, a motor for driving the conveyance rollers, and a sheet discharge unit are disposed separately for each of a document and a recording material.
For that reason, image forming apparatuses have been with unavoidable problems of the increase in complexity of the overall mechanical configuration, the increase in production cost, and the increase in size. To solve those problems, for example, Japanese Patent Application Laid-Open No. 2000-185881 discusses a technique for simplifying the configuration and reducing production cost and size by using a document conveyance path and a recording material conveyance path as a common conveyance path. A document reading unit is disposed in the recording material conveyance path ranging from a sheet feed unit to a sheet discharge unit.
However, in an image forming apparatus discussed in Japanese Patent Application Laid-Open No. 2000-185881, the document reading unit is disposed in the recording material conveyance path, for example, between a fixing device and the sheet discharge unit. Therefore, there has been a problem that, during a document reading operation during which a document exists in the recording material conveyance path, a printing operation for a recording material is suspended, resulting in degraded productivity of the image forming apparatus.
Further, in a case where a plurality of document sheets is read and printing is made on a plurality of recording materials with the configuration discussed in Japanese Patent Application Laid-Open No. 2000-185881, alternately performing the document reading operation and the printing operation will degrade the productivity of recording material printing because of the above-described reason. To avoid that problem, the document reading operation may be performed for all of document sheets prior to the printing operation for recording materials. In this case, however, a mass image memory is required to store all of image data after the document reading operation, resulting in a production cost increase.